1. Field of the Invention
The present invention relates to an adapter ring for rotation of a photographing lens barrel, the adapter ring being fitted into an outer periphery of the photographing lens barrel to rotate a rotation ring of the photographing lens barrel by an operation from the outside.
2. Description of the Related Art
In recent years, with prevailing of outdoor sports, there increase underwater photograph lovers who photograph underwater living things during diving. To perform the photographing in water, a waterproof protector (waterproof case, waterproof housing) is used for a camera such as a digital camera, and a button or a dial of the camera in the waterproof protector is operated via a button or a dial disposed in the waterproof protector.
In a case where a single lens reflex camera equipped with a zoom lens is used during the underwater photographing, a rotation ring such as a zoom ring which is an operation ring disposed in a photographing lens (zoom lens) in the waterproof protector is operated and rotated via a dial (zoom knob) disposed in the waterproof protector.
FIG. 6A is a plan view of a conventional adapter ring 340 for rotation of a photographing lens barrel, and FIG. 6B is a front view of the adapter ring 340. The adapter ring 340 is constituted of a pair of semicircular rings 340L, 340R rotatably connected to each other by a hinge portion 342. An engaging pawl is disposed on a free end (the other end that is not the hinge portion) of one of the semicircular rings 340L, 340R, and an engaging protrusion is disposed on the other free end. The engaging pawl and the engaging protrusion form an engagement portion 344. Moreover, a projecting portion group 340-1 is constituted of a plurality of projecting portions 340-1a which can engage with a ratchet wheel (not shown) disposed in the waterproof protector, and is disposed on an outer periphery of one of the pair of semicircular rings 340L, 340R so that the projecting portions are mutually isometrically arranged around the rotation ring in a predetermined angle range.
In the adapter ring 340 of FIGS. 6A, 6B, the semicircular ring 340L is provided with 15 projecting portions 340-1a which are arranged isometrically in an angle range of 140 degrees. On the other hand, any projecting portion is not disposed on the semicircular ring 340R. It is to be noted that each of constituting members such as the hinge portion 342 and the semicircular rings 340L, 340R is molded of a plastic. When the engagement of the engagement portion 344 is cancelled, the semicircular rings 340L, 340R are released in an arrow direction.
When the above adapter ring 340 is attached to the photographing lens barrel (zoom lens), an operator covers the photographing lens barrel with the opened semicircular rings 340L, 340R, and then engages the engaging pawl formed on one semicircular ring with the engaging protrusion pawl formed on the other semicircular ring. Accordingly, the adapter ring 340 is fitted into the outer periphery of the zoom ring of the photographing lens barrel.
The adapter ring 340 is rotated by the dial (zoom knob) disposed on the waterproof protector. FIG. 7A is a plan view showing the engagement of the ratchet wheel of a dial 322 with the adapter ring 340, and is a diagram showing a state before the engagement. FIG. 7B is a plan view showing an engaging state. The dial 322 includes: a large-diameter dial head 322-1; a shaft portion 322-2 which extends from the dial head 322-1 to pass through a through hole 20Fa of a front cover of the waterproof protector; and a ratchet wheel 322-3 attached to a distant end of the shaft portion. In the dial head 322-1, five projecting portions are formed, and a series of slip stoppers 322-1a are formed on outer peripheries of the projecting portions. The ratchet wheel 322-3 is formed into a disc-like shape, and in the vicinity of the outer periphery of the wheel, a plurality of pawls 322-3a extending in an axial direction of the shaft portion 322-2 are mutually isometrically arranged around an axis of the shaft portion.
In a camera in which the adapter ring 340 is fitted into the outer periphery of the photographing lens barrel, as shown in FIG. 7A, the dial head 322-1 is pulled in the OUT-direction (direction directed externally in a diametric direction of the outer periphery of the photographing lens) to retract the pawls 322-3a of the ratchet wheel 322-3 to a position where the pawls do not collide with the projecting portions 340-1a of the adapter ring. In this state, the camera is stored in the waterproof protector. Moreover, after storing the camera, the dial head 322-1 is pushed in a direction reverse to the OUT-direction, so that the pawls 322-3a of the ratchet wheel 322-3 engage with the projecting portions 340-1a of the adapter ring 340. During the photographing, the pawls 322-3a of the ratchet wheel engage with the projecting portions 340-1a of the adapter ring. Therefore, when the dial head 322-1 is rotated, the ratchet wheel 322-3 is rotated. With the rotation of the ratchet wheel 322-3, the adapter ring 340 rotates together with the zoom ring of the photographing lens barrel. Accordingly, a desired zoom position is set.